JPH10217522A - Thermal head and manufacture of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cracks or separation of a protecting film because of heat or mechanical impact and improve durability, by using as the protecting film for protecting a heat-generating body of a thermal head a film mainly composed of carbon and having a hardness difference in a thicknesswise direction. SOLUTION: A glaze (heat-generating body) of a thermal head 66 is constituted of a glaze layer (heat accumulation layer) 82, a heat-generating resistance body 84, an electrode 86 and a protecting film for protecting the heat-generating resistance body 84, electrode 86, etc., on a substrate 80. The protecting film comprises a lower protecting film 88 formed to cover the heat-generating resistance body 84 and electrode 86 and mainly composed of ceramic, and a carbon protecting film 90 mainly composed of carbon as an upper protecting film on the lower protecting film 88. Because of the presence of the lower protecting film 88, more favorable results are obtained in terms of resistance to wear, corrosion to wear, corrosion and corrosive abrasion, etc. The thermal head is realized with high durability and long life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to various printers,
It belongs to the technical field of a thermal head for performing thermal recording used as a recording means in a plotter, a facsimile, a recorder, and the like.

[0002]

2. Description of the Related Art Thermal recording using a thermal material formed by forming a thermal recording layer using a film or the like as a support is used for recording an ultrasonic diagnostic image. In addition, thermal recording has advantages such as no need for wet development processing and easy handling, and in recent years, in recent years, not only small-sized image recording such as ultrasonic diagnosis but also CT diagnosis and MRI diagnosis have been performed. For applications requiring large and high-quality images, such as X-ray diagnosis and the like, the use for image recording for medical diagnosis is also being studied.

[0003] As is well known, in thermal recording, a heating element having a heating resistor and an electrode, which records an image by heating a thermosensitive recording layer of a thermosensitive material, is arranged in one direction (main scanning direction). Using a thermal head on which a heating element (glaze) is formed, while the glaze is slightly pressed against a thermosensitive material (thermosensitive recording layer), while both are relatively moved in a sub-scanning direction orthogonal to the main scanning direction, According to the image data of the recorded image supplied from an image data supply source such as MRI or CT,
By applying energy to the heating element of each pixel of the glaze to generate heat, the heat-sensitive recording layer of the heat-sensitive material is heated and colored to perform image recording.

In the glaze of this thermal head, a protective film is formed on the surface of the glaze of the thermal head in order to protect the heating element for heating the heat-sensitive material or the electrodes. Therefore,
It is this protective film that comes in contact with the thermosensitive material during thermosensitive recording.
The heating element heats the heat-sensitive material through the protective film, thereby performing heat-sensitive recording. The material of the protective film is usually
Although wear-resistant ceramics and the like are used, the surface of the protective film wears as the recording is repeated because the surface of the protective film slides on the heat-sensitive material in a heated state at the time of heat-sensitive recording.
to degrade.

[0005] If the wear progresses, density unevenness occurs in the thermal image or the strength of the protective film cannot be maintained, so that the function of protecting the heating element and the like is impaired.
Image recording cannot be performed (head shortage). In particular, in applications where high-quality and high-quality multi-gradation images are required, such as in the medical applications described above, a high-rigidity support such as a polyester film is used in order to achieve high quality and high image quality. Using a heat-sensitive film that uses the body,
The recording temperature (applied energy) and the pressing force of the thermal head on the heat-sensitive material are set to be higher. for that reason,
Compared to normal thermal recording, the force and heat applied to the protective film of the thermal head are greater, and wear and corrosion (wear due to corrosion) are more likely to progress.

[0006]

As a method for preventing the abrasion of the protective film of the thermal head and improving the durability, many techniques for improving the performance of the protective film have been studied. As a protective film having excellent wear resistance and corrosion resistance, a protective film containing carbon as a main component (hereinafter referred to as a carbon protective film) is known. For example, Japanese Patent Publication No. Sho 61-53
No. 955 and Japanese Patent Publication No. Hei 4-62866 (divisional application of the above-mentioned application) describe a protective film for a thermal head.
By forming a carbon protective film having a Vickers hardness of 4500 kg / mm ² or more, a thermal head has been disclosed which realizes not only excellent wear resistance but also a sufficiently thin protective film and excellent responsiveness, and a method of manufacturing the same. ing. Japanese Patent Application Laid-Open No. Hei 7-132628 discloses that a protective film having a two-layer structure of a lower silicon-based compound layer and an upper diamond-like carbon layer is provided, thereby significantly reducing wear and destruction of the protective film. A thermal head capable of performing high-quality recording for a long time is disclosed.

[0007] Such a carbon protective film has a characteristic very close to that of diamond, has a very high hardness, and is chemically stable. Therefore, it exhibits excellent characteristics in terms of abrasion resistance and corrosion resistance against sliding contact with a heat-sensitive material. However, the carbon protective film has excellent wear resistance, but is brittle because of its hardness, that is, has low toughness. Therefore, heat shock or thermal stress due to heating of the heating element, stress due to a difference in thermal expansion coefficient between the carbon protective film and a layer in contact with the carbon protective film, and mixing between the heat-sensitive material and the thermal head (glaze) during recording. There is a problem that cracking and peeling occur relatively easily due to mechanical impact or the like caused by foreign matter. If the protective film is cracked or peeled off, wear and corrosion, and even wear due to corrosion will progress from this, and the durability of the thermal head will be reduced, again exhibiting high reliability over a long period of time Can not.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a thermal head having a protective film containing carbon as a main component. And mechanical shock to prevent cracking and peeling of the protective film, have sufficient durability, and demonstrate high reliability over a long period of time. An object of the present invention is to provide a thermal head capable of performing thermal recording stably and a method of manufacturing the thermal head.

[0009]

In order to achieve the above object, a thermal head according to the present invention has a protective film mainly composed of carbon and having a hardness difference in a thickness direction as a protective film for protecting a heating element. A thermal head is provided.

Another aspect of the thermal head of the present invention is to apply a high-frequency bias voltage to the surface of the heating element and change the high-frequency bias voltage in an atmosphere in which a gas containing carbon as a main component is ionized. Accordingly, a thermal head is provided in which a protective film having a hardness difference in the thickness direction is formed on the surface of the heating element.

Further, another aspect of the thermal head of the present invention is to evaporate a solid containing carbon as a main component, generate plasma on the surface of a heating element in an atmosphere into which hydrogen gas is introduced, and apply a high frequency bias voltage. And apply
Further, a thermal head is provided in which a protective film having a hardness difference in a thickness direction is formed on a surface of the heating element by changing a flow rate of the hydrogen gas.

In the thermal head of the present invention, the hardness difference is preferably 100 kg / mm ² or more in Pickers hardness, and a lower protective layer is provided on the heating element side of the protective film containing carbon as a main component. The film preferably has at least one protective film mainly composed of ceramic.

Further, according to the method of manufacturing a thermal head of the present invention, at least a part of a thermal head including a heating element is arranged in a chamber, and a gas containing carbon as a main component flows into the chamber. By applying a high-frequency bias voltage to the surface of the heating element and changing the high-frequency bias voltage, a protective film having a hardness difference in the thickness direction is formed on the surface of the heating element of the thermal head. And a method of manufacturing a thermal head.

Further, another aspect of the method of manufacturing a thermal head according to the present invention is that at least a part of a thermal head including a heating element is disposed in a chamber, and a hydrogen gas is introduced into the chamber while flowing into the chamber. By evaporating a solid containing carbon as a main component, generating plasma on the surface of the heating element, applying a high frequency bias voltage, and changing the flow rate of the hydrogen gas, the thickness of the heating element surface of the thermal head is reduced. A method for manufacturing a thermal head, comprising forming a protective film having a hardness difference in directions.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal head and a method of manufacturing the thermal head according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a schematic view showing an example of a thermal recording apparatus using a thermal head according to the present invention. Thermal recording apparatus 10 shown in FIG. 1 (hereinafter, recording apparatus 10)
Is for performing thermal recording on a heat-sensitive material (hereinafter, referred to as a heat-sensitive material A) which is a cut sheet of a predetermined size such as a B4 size, and a magazine 2 in which the heat-sensitive material A is stored.
The recording unit 20 includes a loading unit 14 into which the recording material 4 is loaded, a supply / transport unit 16, a recording unit 20 that performs thermal recording on the thermal material A by the thermal head 66, and a discharge unit 22.

In such a recording apparatus 10, one heat-sensitive material A is pulled out from the magazine 24, the heat-sensitive material A is conveyed to the recording section 20, and the thermal head 66 is pressed against the heat-sensitive material A while the heating element ( The heat-sensitive material A is transported in the sub-scanning direction orthogonal to the extending direction of the glaze, that is, the main scanning direction (perpendicular to the paper surface in FIGS. 1 and 2), and each heating element is turned on according to the recorded image (image data). By generating heat, heat-sensitive recording is performed on the heat-sensitive material A.

The heat-sensitive material A is a material in which a heat-sensitive recording layer is formed on one surface of a support such as a resin film such as a transparent polyethylene terephthalate (PET) film or paper as a support. Such a heat-sensitive material A is formed into a laminate (bundle) of a predetermined unit of 100 sheets or the like and packaged in a bag, a band, or the like. Are stored in the magazine 24 of the recording apparatus 10, and are taken out one by one from the magazine 24 and provided for thermal recording.

The magazine 24 is a housing having a lid 26 that can be opened and closed. The magazine 24 stores the heat-sensitive material A and is loaded in the loading section 14 of the recording apparatus 10. The loading unit 14 includes the recording device 10
Insertion hole 30 formed in housing 28 of
And guide rolls 34, 34, and a stop member 36. The magazine 24 is inserted into the insertion port 30 with the lid 26 side first.
Then, while being guided by the guide plate 32 and the guide roll 34 and being pushed to a position where it comes into contact with the stop member 36, the recording device 10 is loaded into a predetermined position of the recording device 10. The loading section 14 is provided with an opening / closing mechanism (not shown) for opening and closing the lid 26 of the magazine.

The supply / transportation means 16 is for taking out one heat-sensitive material A from the magazine 24 loaded in the loading section 14 and transporting it to the recording section 20, and uses a suction cup 40 which adsorbs the heat-sensitive material A by suction. Single wafer mechanism, conveyance means 4
2, a transport guide 44, and a pair of regulating rollers 52 located at the exit of the transport guide 44. The conveying means 42 includes a conveying roller 46 and a pulley 4 coaxial with the conveying roller 46.
7a, a pulley 47b and a tension pulley 47c connected to a rotary drive source, an endless belt 48 stretched over the three pulleys, and a nip roller 50 forming a roller pair with the transport roller 46. 40
The leading end of the heat-sensitive material A sheet-fed by the conveying roller 46
And the nip roller 50 to transport the heat-sensitive material A.

When the recording apparatus 10 is instructed to start recording, the lid 26 is opened by the opening / closing mechanism,
The sheet-feeding mechanism using the suction cup 40 takes out one heat-sensitive material A from the magazine 24 and transports the front end of the heat-sensitive material A to the conveying means 42.
(A roller pair composed of the transport roller 46 and the nip roller 50). When the heat-sensitive material A is nipped by the conveyance roller 46 and the nip roller 50, the suction by the suction cup 40 is released, and the supplied heat-sensitive material A is guided by the conveyance guide 44 to the regulating roller pair 52 by the conveyance means 42. Conveyed. When the heat-sensitive material A to be used for recording is completely discharged from the magazine 24, the lid 26 is closed by the opening / closing means.

The distance from the conveying means 42 to the regulating roller pair 52 by the conveying guide 44 is set slightly shorter than the length of the heat-sensitive material A in the conveying direction. The leading end of the heat-sensitive material A reaches the regulating roller pair 52 by carrying by the carrying means 42,
The regulating roller pair 52 is initially stopped, and the leading end of the heat-sensitive material A is temporarily stopped and positioned here. When the tip of the heat-sensitive material A reaches the regulating roller pair 52, the temperature of the thermal head 66 (glaze) is confirmed. If the temperature of the thermal head 66 is a predetermined temperature, the regulating roller pair 5
2, the transfer of the heat-sensitive material A is started.
It is transported to the recording unit 20.

The recording section 20 includes a thermal head 66, a platen roller 60, a cleaning roller pair 56, and a guide 5.
8, a heat sink 67 for cooling the thermal head 66,
It has a cooling fan 76 and a guide 62. The thermal head 66 performs thermal recording at a recording (pixel) density of about 300 dpi, for example, capable of recording an image up to the half cut size. Except for having a characteristic of the protective film, thermal recording on the thermal material A is performed. Heating element is one direction (main scanning direction)
Has a known configuration in which glazes are arranged. A heat sink 67 for cooling is fixed to the thermal head 66. The thermal head 66 is supported by a support member 68 that is rotatable up and down around a fulcrum 68a. This thermal head 66
Will be described later in detail. The width (main scanning direction), resolution (recording density), recording gradation and the like of the thermal head 66 of the present invention are not particularly limited, but the width is 5 cm to 5 cm.
Preferably, the recording density is 50 cm, the resolution is 6 dot / mm (about 150 dpi) or more, and the recording gradation is 256 or more.

The platen roller 60 rotates in a direction indicated by an arrow in the figure at a predetermined image recording speed while holding the heat-sensitive material A at a predetermined position, and rotates in a sub-scanning direction orthogonal to the main scanning direction (the direction indicated by an arrow X in FIG. 2). ) To transport the heat-sensitive material A. The cleaning roller pair 56 is a roller pair comprising an adhesive rubber roller (upper side in the figure) which is an elastic body and a normal roller. The adhesive rubber roller removes dust and the like adhered to the heat-sensitive recording layer of the heat-sensitive material A, It prevents dust from adhering to the glaze and adversely affecting image recording.

In the illustrated recording apparatus 10, before the heat-sensitive material A is conveyed, the support member 68 rotates upward,
This is a standby position immediately before the glaze of the thermal head 66 comes into contact with the platen roller 60. When the conveyance by the above-described regulating roller pair 52 is started, the heat-sensitive material A
Next, it is nipped by the cleaning roller pair 56,
It is transported while being guided by the guide 58. When the leading end of the heat-sensitive material A is conveyed to the recording start position (the position corresponding to the glaze), the support member 68 rotates downward, and the heat-sensitive material A is sandwiched between the glaze and the platen roller 60,
The glaze is pressed against the recording layer, and the heat-sensitive material A
While being held at a predetermined position by the platen roller 60, the sheet is transported in the sub-scanning direction by the platen roller 60 and the like.
With this conveyance, each of the glaze heating elements is heated according to the recorded image, so that thermal recording is performed on the thermal material A.

The heat-sensitive material A on which the heat-sensitive recording has been completed is conveyed to the platen roller 60 and the conveying roller pair 63 while being guided by the guide 62, and is discharged to the tray 72 of the discharge section 22. The tray 72 protrudes outside the recording apparatus 10 through a discharge port 74 formed in the housing 28, and the heat-sensitive material A on which an image is recorded is discharged to the outside through the discharge port 74 and is taken out.

FIG. 2 is a schematic sectional view of the glaze (heating element) of the thermal head 66. In the illustrated example, the glaze is on the substrate 80 (the thermal head 66 in the illustrated example).
Is pressed by the heat-sensitive material A from above, so that it is formed in a lower layer in FIG. 2), a heat-generating resistor 84 formed thereon, and a heat-generating resistor 84 formed thereon. And a protective film for protecting the heating resistor 84 or the electrode 86 and the like formed thereon. In the illustrated example, as a preferred embodiment, the protective film has a two-layer structure, and includes a lower protective film 88 mainly composed of ceramic, which is formed so as to cover the heating resistor 84 and the electrode 86 (heating element). Protective film 88
A protective film composed of a protective film containing carbon as a main component, that is, a carbon protective film 90 (DLC protective film = Diamond Like Carbon protective film), which is a characteristic part of the present invention, is formed as an upper protective film on the substrate. Be composed.

Thermal head 66 used in the present invention
Has basically the same configuration as the known thermal head 66 except for the carbon protective film 90. Therefore, there is no particular limitation on the other layer configuration and the material of each layer, and various known materials can be used. Specifically, the substrate 80 is made of an electrically insulating material such as heat-resistant glass or ceramics such as alumina, silica, or magnesia, and the glaze layer 82 is made of a heat-resistant glass or heat-resistant resin such as a polyimide resin. Nichrome (Ni-C
r), a heating resistor such as tantalum or tantalum nitride
As the material 6, various conductive materials such as aluminum and copper can be used. In addition, vacuum deposition, CVD
(Chemical Vapor Deposition), a thin-film type heating element formed by using a so-called thin film forming technique such as sputtering and a photo-etching method, and a so-called thick film forming technique by screen printing and firing and formed by using a so-called thick film forming technique and etching Although a thick film type heating element is known, the thermal head 66 used in the present invention may be formed by any method.

As described above, the thermal head 6 in the illustrated example
6 has a two-layered protective film of a carbon protective film 90 and a lower protective film 88 as a preferred embodiment. By having such a lower protective film, it is possible to obtain more favorable results in terms of wear resistance, corrosion resistance, corrosion wear resistance, and the like,
A more durable, long-life thermal head can be realized. As the lower protective film 88 formed on the thermal head 66 of the present invention, various known materials can be used as long as the lower protective film 88 has heat resistance, corrosion resistance, and wear resistance that can be a protective film of the thermal head. However, preferably, a lower protective film 88 mainly composed of ceramics is exemplified.

Specifically, silicon nitride (SiN), silicon carbide (S
iC), tantalum oxide (Ta ₂ O ₅ ), aluminum oxide (Al
₂ O ₃ ), Sialon (SiAlON), silicon oxide (SiO ₂ ), aluminum nitride (AlN), boron nitride (BN), selenium oxide (SeO)
, Titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), chromium nitride (CrN), and mixtures thereof. Among them, silicon nitride, silicon carbide, sialon, and the like are preferably used from the viewpoint of ease of film formation, manufacturing adequacy such as manufacturing cost, balance between mechanical wear and chemical wear, and the like. Further, the lower protective film may contain a small amount of an additive such as a metal for adjusting physical properties.
There is no particular limitation on the method of forming the lower protective film 88, and the lower protective film 88 is formed by a known method of forming a ceramic film (layer) using the above-described thick film forming technology, thin film forming technology, or the like.

The thickness of the lower protective film 88 is not particularly limited, but is preferably about 2 μm to 50 μm, and more preferably about 4 μm to 20 μm. By setting the thickness of the lower protective film 88 within the above range, a favorable result can be obtained in that a balance between abrasion resistance and thermal conductivity (that is, recording sensitivity) can be appropriately obtained. Further, the lower protective film 88 may have a multilayer structure. When the lower protective film 88 has a multi-layer structure, the lower protective film 88 may have a multi-layer structure using different materials, or may have a multi-layer structure having different layers of the same material with different densities or both. It may be something.

Incidentally, the thermal head of the present invention is not limited to the one having such a lower protective film 88, and the protective film may have a single-layer structure of only a carbon protective film 90 described later.

The thermal head 66 of the present invention has a carbon protective film 90 as a protective film for protecting the heating resistor 84 and the like.
And the carbon protective film 90
Is that the hardness on the heating resistor 84 side (inside) is lower than the surface side (contact side with the heat-sensitive material A), or the hardness on the inside is higher than that on the surface side. It has a hardness gradient in the thickness direction. With such a configuration, the excellent abrasion resistance and corrosion resistance of the carbon protective film 90 can be sufficiently exhibited, and the above-described heat shock, thermal stress, and the lower layer (the lower protective film 8 in the illustrated example) can be obtained.
8) It is possible to prevent the carbon protective film 90 from being cracked or peeled off due to stress due to a difference in thermal expansion coefficient from that of 8) or mechanical shock due to impurities, and to realize a thermal head with excellent durability.

In the thermal head 66 of the present invention, the hardness difference between the surface and the inside of the carbon protective film 90 is not particularly limited. In order to stably realize the above, the difference in hardness is preferably 100 kg / mm ² or more, particularly 500 kg / mm ² or more in Vickers hardness. The upper limit of the difference in hardness is not particularly limited. However, if the difference in hardness is too large, inconveniences such as cracking or peeling from a soft portion may easily occur during thermal recording. 2000 kg / mm ² or less, especially 150
It is preferably 0 kg / mm ² or less. That is, in the present invention, the hardness difference between the surface and the inside of the carbon protective film 90 is preferably in the range of ^{100kg / mm 2 ~2000kg / mm 2} ,
More preferably in the range of ^{500kg / mm 2 ~1500kg / mm 2} .

The change in the hardness of the carbon protective film 90 in the thickness direction may be continuous or stepwise.
However, in consideration of cracking or peeling inside the carbon protective film 90, it is preferable that the change in hardness in the thickness direction is continuous. In the case where the carbon protective film 90 has a stepwise change, it is equivalent to the carbon protective film 90 having a multilayer structure.
In order to reduce cracking, peeling, and the like, it is preferable that the hardness difference between the layers is small.

The higher the hardness of the carbon protective film 90 is, the better it is. It is sufficient that the carbon protective film 90 has a sufficient hardness as a protective film of the thermal head. Preferably, the hardness of the hardest part is 2000 kg / Pickers hardness. mm ² or more, more preferably 2500 kg / mm ² or more, particularly preferably 3000
kg / mm ² or more. By setting the hardness of the carbon protective film 90 within the above range, favorable results can be obtained in terms of abrasion resistance and the like.

Further, the thickness of the carbon protective film 90 is not particularly limited. When the lower protective film 88 is provided as shown in the figure, the thickness is preferably 0.1 μm to 5 μm, more preferably 1 μm to 5 μm. 3 μm. Also, the lower protective film 8
8 is preferably 1 μm to 20 μm.
m, more preferably 2 μm to 10 μm. By setting the thickness of the carbon protective film 90 within the above range, favorable results can be obtained in terms of the balance between wear resistance and thermal conductivity.

The method of forming the carbon protective film 90 is not particularly limited, and is formed by a known thick film forming technique or thin film forming technique. Preferably, the carbon protective film 90 is formed by plasma CVD using a hydrocarbon gas as a reaction gas. A method of forming a hard carbon film and a method of forming a hard carbon film by sputtering using a carbon material such as a sintered carbon material or a glassy carbon material as a target material are exemplified.

FIG. 3 is a conceptual diagram of a (plasma) CVD apparatus for forming the carbon protective film 90. CVD equipment 1
Basically, reference numeral 00 denotes a vacuum chamber 102, a gas introduction unit 104, a plasma generation unit 106, and a substrate holder 10.
8 and a substrate bias power supply 110.

The vacuum chamber 102 is preferably formed of a non-magnetic material such as SUS 304 so that the magnetic field for generating plasma is not affected. Also, the carbon protective film 9
The vacuum chamber 102 used for forming 0 has an exhaust means, and the ultimate pressure of the initial exhaust is 2 × 10 ⁻⁵ Torr or less, preferably 5 × 10 ⁻⁶ Torr or less. It is preferable to have a sealing property to attain from × 10 ⁻⁴ Torr to 1 × 10 ⁻² Torr. As the evacuation unit 112 attached to the vacuum chamber 102, an evacuation unit combining a rotary pump, a mechanical booster pump, and a turbo pump is preferably exemplified, and an evacuation unit using a diffusion pump or a cryopump instead of the turbo pump may also be used. It is preferably used. The evacuation capacity and the number of evacuation means 112 may be appropriately selected according to the volume of the vacuum chamber 102, the type and flow rate of gas used for film formation, and the like. In addition, in order to adjust the exhaust speed, the exhaust speed may be adjusted by adjusting the exhaust resistance of the pipe using a bypass pipe, or by providing an orifice valve and adjusting the opening degree thereof. .

In the vacuum chamber 102, a portion where an arc is generated by plasma or an electromagnetic wave for generating plasma may be covered with an insulating member. As an insulating member,
MC nylon, Teflon (PTFE), PPS (polyphenylene sulfide), PEN (polyethylene naphthalate), PET (polyethylene terephthalate) and the like can be used. When using PEN, PET, or the like, care must be taken when using such a material because the degree of vacuum may be reduced by degassing from the insulating member.

The CVD apparatus 100 has two gas introduction sections 1
04. The gas introduction part 104a is a part for introducing a gas for plasma generation, while the gas introduction part 104b
Is a portion for introducing a reaction gas, and a gas is introduced into the vacuum chamber 102 using a stainless steel pipe or the like whose introduction portion is vacuum-sealed with an O-ring or the like. Further, the amount of gas introduced is controlled by a known method such as a mass flow controller. The two gas introduction units 104 are basically configured to wipe off gas to the vicinity of the plasma generation region in the vacuum chamber 102. Further, since the blowing position, particularly the blowing position of the reactive gas introduction portion 104b, also affects the film thickness distribution, it is preferable to optimize the blowing position according to the shape of the substrate (glaze of the thermal head 66).

As a gas for generating plasma for forming the carbon protective film 90, for example, an inert gas such as helium, neon, argon, krypton, or xenon is used. In this respect, argon gas is preferably used. On the other hand, as a reaction gas for forming the carbon protective film 90, a gas of a hydrocarbon compound such as methane, ethane, propane, ethylene, acetylene, and benzene is exemplified. Note that both the gas introduction unit 104a and the gas introduction unit 104b need to adjust (calibrate) the sensor of the mass flow controller according to the gas used.

The carbon protective film 90 (the carbon protective film 9)
In plasma CVD for forming 0), a DC glow discharge, a high-frequency discharge, a DC arc discharge, a microwave ECR discharge, or the like can be used as a plasma generating means. In particular, the DC arc discharge and the microwave ECR discharge have a plasma density. And is advantageous for high-speed film formation. CV in the example shown
The D device 100 utilizes microwave ECR discharge, and the plasma generating means 106 includes a microwave power source 1
14, a magnet 116, a microwave waveguide 118, a coaxial converter 120, a dielectric plate 122, a radial antenna 124, and the like.

The DC glow discharge generates a plasma by applying a negative DC voltage between the substrate and the electrode. A DC power supply used for the DC glow discharge is about 1 kW to 10 kW, and a DC power supply having a necessary and sufficient output for forming the carbon protective film 90 may be appropriately selected. Further, a DC power supply pulse-modulated at 2 kHz to 20 kHz can be suitably used in terms of arc prevention and the like. High frequency discharge is
Plasma is generated by applying a high-frequency voltage to the electrodes via the matching box. In that case, perform impedance matching with a matching box,
The reflection is adjusted so that the reflected wave of the high-frequency voltage is 25% or less of the incident wave. As a high-frequency power source for performing high-frequency discharge, a power source having a sufficient output required for forming the carbon protective film 90 may be appropriately selected within a range of 1 to 10 kW at 13.56 MHz for industrial use. Also, a pulse-modulated high-frequency power supply can be used.

DC arc discharge uses a hot cathode to generate a plasma. As the hot cathode, tungsten, lanthanum boride (LaB ₆ ), or the like can be used. DC arc discharge using a hollow cathode can also be used.
As a DC power supply used for DC arc discharge, 1 kW to 1
In the range of about 0 kW and about 10 A to 200 A, what has a sufficient output necessary and necessary for forming the carbon protective film 90 may be appropriately selected.

The microwave ECR discharge is performed by using microwave and E
A plasma is generated by the CR magnetic field,
As described above, the illustrated CVD apparatus 100 generates plasma by the microwave discharge. The microwave power supply 114 is an industrial 2.45 GHz, 1 k
In the range of about W to 3 kW, a film having a sufficient output necessary and necessary for forming the carbon protective film 90 may be appropriately selected. For generating the ECR magnetic field, a permanent magnet or an electromagnet capable of forming a desired magnetic field may be used as appropriate. In the illustrated example, an Sm-Co magnet is used as the magnet 116. For example, when a microwave of 2.45 GHz is used, E
Since the CR magnetic field is 875 G (Gauss), a magnet having a magnetic field of 500 G to 2000 G in the plasma generation region may be used. The introduction of microwaves into the vacuum chamber 102 is performed using a microwave waveguide 118, a coaxial converter 120, a dielectric plate 122, and the like. Since the state of formation of the magnetic field and the introduction path of the microwave affect the film thickness distribution of the carbon protective film 90, it is preferable to optimize the carbon protective film 90 so that the film thickness becomes uniform.

The substrate holder 108 is provided with a thermal head 66 having a heat sink 67, a thermal head 66 having no heat sink 67, a portion including a glaze removed from the thermal head 66, and the like by known fixing means such as a clamp and a jig. , And the glaze serving as a substrate for film formation is fixed facing the radial antenna 124. Further, the glaze may be configured to be rotatable or movable with respect to the plasma generating means 106 as necessary.
The distance between the substrate (glaze surface) and the radial antenna 124 (plasma generating portion) is not particularly limited, and is 20 mm to 20 mm.
A distance at which the film thickness distribution becomes uniform may be selected and set within a range of about 0 mm. When forming the carbon protective film 90, a mask for regulating the film formation region may be used as necessary. In this case, for example, a plate-shaped mask member made of a metal such as SUS304 or aluminum or a resin such as Teflon may be manufactured, and the non-film-formed portion may be masked using this.

In order to obtain a carbon film by plasma CVD, it is necessary to form a film while applying a negative bias voltage to the substrate. The substrate bias power supply 110 is for applying this bias voltage. There is no particular limitation,
Since the carbon protective film 90 has a high electric resistance value, it is preferable to use a self-bias voltage of a high-frequency voltage. The self-bias voltage is a negative direct current component generated when a high-frequency voltage is applied in plasma. When a carbon film is formed, the self-bias voltage is usually about -100 V to -500 V. The high-frequency power supply may be appropriately selected from those of 13.56 MHz for industrial use and about 1 kW to 5 kW. When a high-frequency voltage is applied to the substrate, it is preferable to use a matching box for matching impedance between the substrate and the high-frequency power supply. The matching box may be controlled manually or automatically, and various off-the-shelf products can be used. further,
In addition to the self-bias voltage of the high-frequency voltage, 2 kHz to 2
A DC power supply pulse-modulated to 0 kHz can also be used.
Also in this case, the applied voltage is about -100V to -500V.

Here, in plasma CVD, the hardness of the carbon protective film 90 to be generated can be adjusted by adjusting the substrate bias voltage. In general, a carbon film formed by CVD while applying a substrate bias voltage has a higher hardness as the substrate bias voltage goes from 0 to a negative value, and has the highest hardness in the range of -200 V to -300 V. If the value exceeds this, the hardness decreases. Therefore, for example, by setting the substrate bias voltage at the start of film formation to about −100 V and gradually changing it to −300 V by the end of film formation, a somewhat soft film is formed at the start of film formation, At the end of the film formation, the carbon protective film 90 having the hardness difference, that is, the hardness gradient in the thickness direction, in which the film becomes the hardest and the hardness increases from the inner side (heating element side) toward the surface, can be formed. Conversely, by setting the substrate bias voltage to about -300 V at the start of film formation and changing it to -100 V by the end of film formation, the carbon protective film 90 whose hardness increases from the surface toward the inside is increased.
Is obtained. At this time, if the substrate bias voltage is continuously changed, the hardness of the carbon protective film 90 is continuously changed, and by changing the substrate bias voltage stepwise, a stepwise hardening equivalent to a multilayer structure is obtained. This results in a carbon protective film 90 having a change in thickness.

The method of setting and controlling the hardness and hardness difference of the carbon protective film 90 to be formed is not particularly limited. For example, the relationship between the substrate bias voltage and the hardness of the film is examined in advance by experiments or the like. The substrate bias voltage at the time of forming the carbon protective film 90 is adjusted accordingly,
What is necessary is just to produce | generate the carbon protective film 90 which has desired hardness and a hardness difference (hardness gradient).

As a method of adjusting the hardness of the carbon protective film 90, a method of adjusting the hydrogen content in the film is also exemplified. Using hydrocarbon gas as reaction gas
In the illustrated embodiment in which the carbon protective film 90 is formed by CVD, a film having the highest hardness can be obtained when the hydrogen content in the film is around 30% by atomic ratio. Therefore, by selecting the reaction gas according to the amount of hydrogen atoms in the molecule, the carbon protective film 90 having a difference in hardness can be formed.

In the present invention, in order to improve the adhesion of the carbon protective film 90, prior to the formation of the carbon protective film 90, the surface of the substrate (glaze), ie, the surface of the lower protective film 88 in FIG. It is preferable to perform etching. As an etching method, a method of applying a high-frequency voltage through a matching box while generating plasma by the plasma generating means 106, or a method of directly generating plasma by the high-frequency voltage and performing etching using the plasma A method is illustrated. 13.56 MHz for industrial use as high frequency power supply
Therefore, it may be appropriately selected from those of about 1 kW to 5 kW. Further, the etching strength may be determined by using a bias voltage applied to the substrate as a guide.
In this range, optimization may be appropriately performed.

FIG. 4 is a conceptual diagram of a sputtering apparatus for forming the carbon protective film 90. The sputtering apparatus 130 basically includes a vacuum chamber 132, a gas introduction unit 134, a sputtering unit 136, and a substrate holder 138.

The vacuum chamber 132 for performing the sputtering for forming the carbon protective film, the evacuation means 140 attached thereto, and the means for adjusting the evacuation speed are basically the same as those in the CVD apparatus 100 and have the same structure. Are preferably exemplified.

The gas introduction part 134 is a part for introducing a gas for generating plasma and a hydrogen gas, and has a gas introduction part 134a for plasma generation and a gas introduction part 134b for hydrogen gas. In both cases, similarly to the gas introduction unit 104 of the CVD apparatus 100, the introduction amount is controlled by a known method such as a mass flow controller using a stainless steel pipe or the like which is vacuum-sealed with an O-ring or the like. Gas is introduced into The gas is configured to be wiped out in the vicinity of the plasma generation region in the vacuum chamber 132. Further, it is preferable to optimize the blowing position so as not to affect the distribution of the generated plasma.
As a gas for plasma generation for producing the carbon protective film 90, for example, helium, neon, argon,
Inert gases such as krypton and xenon are used,
Among them, argon gas is particularly preferably used in terms of cost and availability.

Here, in this embodiment in which sputtering is used to form the carbon protective film 90, the hardness of the film is reduced by flowing a hydrogen gas together with a gas for generating plasma and adjusting the flow rate thereof. Can be adjusted. Therefore, by changing the flow rate of hydrogen gas during film formation, the carbon protective film 90 having a hardness difference (hardness gradient) between the surface and the inside can be manufactured. For example,
When argon is used as the plasma generating gas, a film having the highest hardness can be formed when the flow rate of the hydrogen gas is 5% to 10% of the argon flow rate, and the film is formed as the amount of hydrogen increases. Softens. Therefore, for example, by setting the hydrogen gas flow rate at the start of film formation to about 20% of the argon gas and gradually changing it to about 5% by the end of film formation, the same as in the above-described plasma CVD example In addition, it is possible to form the carbon protective film 90 having a hardness gradient in which the hardness increases from the inside toward the surface. Conversely, by setting the flow rate of hydrogen gas at the start of film formation to about 5% of that of argon gas and changing it to about 20% by the end of film formation, carbon whose hardness increases from the surface toward the inside is increased. A protective film 90 can be formed. Similarly, if the hydrogen inflow is continuously changed, the hardness of the carbon protective film 90 is continuously changed, and if the hydrogen inflow is changed stepwise, the hardness is gradually changed.

The method of setting and controlling the hardness of the carbon protective film 90 is not particularly limited. For example, the relationship between the flow rate of hydrogen gas and the hardness of the film is examined in advance by experiments or the like.
The hydrogen gas flow rate during film formation is adjusted accordingly,
What is necessary is just to produce | generate the carbon protective film 90 which has desired hardness and a hardness difference (hardness gradient). The carbon protective film 9
Considering a hardness of 0 or the like, for example, when argon is used as the plasma generating gas, the hydrogen gas flow rate is preferably in the range of 2% to 50% of the argon gas flow rate.
It is preferable that the inflow of the hydrogen gas be performed through an introduction pipe independent of the plasma generation gas as shown in the illustrated example. It may be performed with a book introduction pipe.

In the sputtering, a target material 144 to be sputtered is disposed on the cathode 142, the cathode 142 is set to a negative potential, and plasma is generated on the surface of the target material 144, so that the target material 144 (its atoms) is ejected. A film is formed by adhering to and depositing on the surface of the substrate (the glaze surface of the thermal head 66 in the illustrated example = the surface of the lower protective film 88). The sputtering means 136 includes the cathode 142, the arrangement portion of the target material 144, a shutter 146, a DC power supply 152, and the like.

When generating plasma on the surface of the target material 144, the negative side of the DC power supply 152 is directly connected to the cathode 142, and a DC voltage of about -300V to -1000V is applied. As an output of the DC power supply 152,
In the range of about 1 kW to 10 kW, the carbon protective film 9
What has output sufficient for formation of 0 may be appropriately selected. Note that the shape of the cathode 142 is the same as that of the carbon protective film 9.
What is necessary is just to determine suitably according to the shape of the board | substrate in which 0 is formed, etc. In addition, in terms of arc prevention, etc., 2 kHz to 20 kHz
It is also possible to suitably use a negative DC power supply that has been pulse-modulated. In addition, a high frequency power supply can be used to generate plasma. When a high-frequency power supply is used, plasma is generated by applying a high-frequency voltage to the cathode 142 via the matching box. At this time, impedance matching is performed by a matching box, and adjustment is performed so that the reflected wave of the high-frequency voltage is 25% or less of the incident wave. As a high frequency power supply, 13.56 for industrial use
In the range of about 1 kW to about 10 kW in MHz, a material having a sufficient output necessary and necessary for forming the carbon protective film 90 may be appropriately selected.

The target material 144 may be directly fixed to the cathode 142 using In-based solder or mechanical fixing means, but usually, a backing plate 154 made of oxygen-free copper, stainless steel, or the like is fixed to the cathode 142. Then, the target material 144 is attached thereon as described above. In addition, the cathode 142 and the backing plate 1
54 is configured to be water-coolable, whereby the target material 144 is also indirectly water-cooled. The carbon protective film 9
Preferable examples of the target material 144 used for forming 0 include a sintered carbon material, a glassy carbon material, and the like. Further, the shape may be appropriately determined according to the shape of the substrate.

The carbon protective film 90 is formed on the cathode 1
Magnetron sputtering, in which a magnet 148 such as a permanent magnet or an electromagnet is disposed inside 42 and a magnetic field is formed on the surface of the target material 144 to confine plasma and perform sputtering, can also be suitably used. This magnetron sputtering is preferable in that the film forming speed is high. The shape, position and number of the permanent magnets and electromagnets, the intensity of the generated magnetic field, and the like are appropriately determined according to the thickness and thickness distribution of the carbon protective film 90 to be formed, the shape of the target material 144, and the like. Further, it is preferable to use a magnet capable of generating a high magnetic field such as a Sm-Co magnet or a Nd-Fe-B magnet as the permanent magnet since plasma can be sufficiently confined.

The substrate holder 138 is provided with the above-described CVD apparatus 1.
00, and is basically the same as the substrate holder 108 disposed at
The glaze serving as a substrate is fixed facing the cathode 142. Also, if necessary, the cathode 1
The glaze may be configured to be rotatable or movable with respect to 42, and may be appropriately selected according to the size of the substrate or the like. The distance between the substrate and the target material 144 is not particularly limited,
The distance at which the film thickness distribution becomes uniform may be selected and set within a range of about 20 mm to 200 mm.

In order to obtain the carbon protective film 90,
Film formation is performed while applying a negative bias voltage to the substrate (the lower protective film 88 in the illustrated example). The bias power supply 150 is for this purpose. The bias voltage is not particularly limited, but it is preferable to use a high-frequency voltage self-bias voltage as in the case of the CDV. As the high-frequency power supply, the same as the above-mentioned CVD can be used, and it is also preferable to use a matching box. Furthermore, besides the self-bias voltage of the high frequency voltage, 2 kHz
A DC power supply pulse-modulated to ２０20 kHz is also available. Also in this case, the applied voltage is about -100V to -500V.

When the carbon protective film 90 is formed, in order to improve the adhesion between the carbon protective film 90 and the lower layer (lower protective film 88), the lower protective film 88 is formed before the carbon protective film 90 is formed. Preferably, the surface is etched with plasma. Examples of the etching method include a method in which plasma is generated and a high-frequency voltage is applied to the substrate via a matching box, and a method in which plasma is directly generated by the high-frequency voltage and the plasma is used. What is necessary is just to use what was mentioned above for generation of plasma and a high frequency power supply. The etching strength may be determined by using a bias voltage applied to the substrate as a guide.
Optimization may be appropriately performed in the range of 500 V.

As described above, the thermal head and the method of manufacturing the same according to the present invention have been described in detail. However, the present invention is not limited to the above-described example, and various improvements and changes may be made.

[0067]

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. [Embodiment 1] (Plasma) CVD apparatus 1 shown in FIG.
00 was prepared. Details are as follows.

A. Vacuum chamber 102 SUS304 having, as evacuation means 112, a rotary pump having an evacuation speed of 1500 L (liter) / min, a mechanical booster pump having an evacuation speed of 12,000 L / min, and a turbo pump having an evacuation speed of 3000 L / sec.
Vacuum chamber 102 having a capacity of 0.5 m ³ . An orifice valve is arranged in the suction part of the turbo pump so that the opening degree can be adjusted from 10 to 100%.

B. The gas introduction unit 104 was configured using a mass flow controller having a maximum flow rate of 100 to 500 [sccm] and a stainless steel pipe having a diameter of 6 mm. The joint between the stainless steel pipe and the vacuum chamber 102 was vacuum-sealed with an O-ring. Argon gas was used as the plasma generation gas.

C. Plasma generating means 106 A microwave ECR plasma generating apparatus using a microwave power supply 114 having an oscillation frequency of 2.45 GHz and a maximum output of 3.0 kW was used. The microwave is supplied to the microwave introduction tube 118.
To the vicinity of the vacuum chamber 102 and the coaxial converter 120
After the conversion, the radial antenna 12 in the vacuum chamber 102
4 was introduced. The dielectric plate 122 has a width of 800 mm and a height of 2 mm.
A 00 mm rectangular one was used. The microwave is divided into four parts in the middle of the microwave introduction tube 118 and the dielectric plate 12
2 were introduced into the vacuum chamber 102 from four places. Furthermore, a magnetic field for ECR was formed by arranging a plurality of Sm-Co magnets as the magnets 116 according to the shape of the dielectric plate 122.

D. Substrate Holder 108 The substrate (that is, the glaze of the thermal head 66) is held so as to face the plasma generator, and the distance between the target material 114 and the radial antenna 124 is adjustable between 50 mm and 150 mm. Further, the holding portion of the thermal head by the substrate was set to a floating potential so that a high frequency voltage for etching could be applied.

E. Substrate bias power supply 110 A high frequency power supply was connected to the substrate holder 108 as a substrate bias power supply 110 via a matching box. The high frequency power supply has a frequency of 13.56 MHz and a maximum output of 3 k
W. The high-frequency power supply is configured so that the high-frequency output can be adjusted in a range of -100 V to -500 V by monitoring a self-bias voltage. In the CVD apparatus 100, the substrate biasing means 110
Also serves as a substrate etching means.

<Production of Thermal Head> Such a CV
Using the D apparatus 100, a thermal head was manufactured as described below. Kyocera KGT-260-12MPH8 was used as a base thermal head. In this thermal head, an 11 μm thick silicon nitride film (Si ₃ N ₄ ) is formed as a protective film on the glaze surface. Therefore, in this embodiment, this silicon nitride film becomes the lower protective film 88, and the thermal head 66 having a two-layer protective film in which the carbon protective film 90 is formed thereon.

First, the vacuum chamber 1 is set so that the glaze of the thermal head faces the radial antenna 124.
The thermal head was fixed to the substrate holder 108 in the substrate No. 02. The distance between the substrate (glaze surface) and the radial antenna 124 was 100 mm. In addition, masking was previously performed on portions other than the portion where the carbon protective film of the thermal head was formed (that is, other than glaze). After fixing the thermal head, the pressure in the vacuum chamber 102 becomes 5 × 10
Evacuated to ^-6 Torr. While continuing the vacuum evacuation, an argon gas is introduced by the gas introduction unit 104a, and the pressure in the vacuum chamber 102 is set to 1.0 × 10 ⁻³ Torr by an orifice valve installed in a turbo pump.
It was adjusted to become. Next, the microwave power supply 114
, And microwaves are introduced into the vacuum chamber 102 from four locations by 400 W each to generate microwave ECR plasma. Further, the substrate bias power supply 110 is driven to apply a high frequency bias voltage to the substrate. The lower protective film 88 (silicon nitride film) was etched at a self-bias voltage of -200 V for 2 minutes. After the etching is completed, the pressure in the vacuum chamber 102 is increased to 3.0 × 10 while the application of the high frequency bias voltage by the self-bias voltage is continued.
Plasma CV by introducing methane gas to ^-3 Torr
D was performed to produce a thermal head 66 having a carbon protective film 90 having a thickness of 1 μm. Further, a thermal head having a carbon protective film 90 having a thickness of 2 μm and 3 μm was manufactured in exactly the same manner.

Here, in the above example, the relationship between the hardness of the carbon protective film 90 formed by this system and the self-bias voltage at the time of film formation is examined in advance, and the carbon protective film 90 is formed accordingly. The hardness and hardness difference of the carbon protective film 90 were controlled. More specifically, in any of the film thicknesses of 1 μm, 2 μm, and 3 μm, the self-bias voltage is continuously changed so that the self-bias voltage at the start of film formation is −100 V and −200 V at the end of film formation. The Vickers hardness at the start of film formation (inside) is 1500
kg / mm ² , Vickers hardness at the end of film formation (surface) is 250
Of 0 kg / mm ^2, hardness difference was formed a carbon protective film 90 that changes continuously hardness 1000 kg / mm ^2. Further, the film thickness of the carbon protective film 90 was controlled in advance by calculating a film forming speed, calculating a film forming time to obtain a predetermined film thickness, and controlling the film forming time.

<Evaluation of Performance> Using these three types of thermal heads of the present invention and a thermal material (dry image recording film CR-AT manufactured by FUJIFILM Corporation), a thermal recording test of 5000 sheets of B4 size was performed. went. As a result, the thickness of the carbon protective film 90 is 1 μm, 2 μm and 3 μm.
In any of the thermal heads, the carbon protective film 90 did not crack or peel off, and hardly any wear was observed.

Example 2 Three types of thermal protective films having carbon protective films 90 having thicknesses of 1 μm, 2 μm and 3 μm, respectively, were obtained in the same manner as in Example 1 except that the reaction gas was changed to acetylene gas. A head was manufactured. The hardness of the carbon protective film 90 and the difference in hardness were controlled in the same manner as in the first embodiment. Specifically, in any of the three types of thermal heads, the self-bias voltage is continuously changed so that the self-bias voltage at the start of film formation is -100 V and at the end of film formation is -200 V. Vickers hardness at the start of film formation (inside) is 1500 kg
/ mm ² , Vickers hardness at the end of film formation (surface) is 2500
of kg / mm ^2, hardness difference is set to continuously carbon protective film 90 hardness changes at 1000 kg / mm ^2.

<Evaluation of Performance> Using the three types of thermal heads of the present invention, the same performance evaluation as in Example 1 was performed. As a result, none of the thermal heads causes cracking or peeling of the carbon protective film 90.
Almost no wear was observed.

Further, the same performance evaluation test was performed without performing etching;
2 at 0.8 × 10 ^-3 Torr and 5.0 × 10 ^-3 Torr
Change to Torr; or vacuum chamber 10 during film formation
2 only at 2.0 × 10 ^-3 Torr and 5.0 × 1
Change to 0 ^-3 Torr; and otherwise in the same manner, in the same manner as in Example 1 and Example 2 was prepared by forming 1 [mu] m, a 2μm and 3μm carbon protective film 90 of,
Various types of thermal heads were also used. In each case, the same good results as in Examples 1 and 2 were obtained.

Example 3 A sputtering apparatus 130 shown in FIG. 4 was prepared. The vacuum chamber 132,
The gas introduction part 134 and the substrate holder 138 are the same as those in the first embodiment. Other details are as follows.

A. Sputtering means 106 A rectangular cathode 142 having a target material size of 600 mm in width and 100 mm in height, in which an Sm-Co magnet was disposed as the magnet 148, was used. As the backing plate 154, a sintered carbon material processed into a rectangular shape was used, and was bonded to the cathode 142 using In-based solder. Also,
By cooling the inside of the cathode 142 with water, the magnet 14
8, the cathode 142 and the back surface of the backing plate 154 were cooled. Maximum output 8kW as DC power supply 152
, And the negative side was connected to the cathode 142. In addition, this DC power supply is 2 kHz to 10 kHz.
The pulse width can be modulated within the range described above.

B. Bias power supply 150 A high frequency power supply was connected to the substrate holder 138 via a matching box. The high frequency power supply has a frequency of 13.56M
At Hz, the maximum power is 3 kW. This high-frequency power supply monitors the self-bias voltage to obtain -1
The high frequency output is configured to be adjustable in the range of 00V to -500V. The bias power supply 150 also serves as an etching unit.

<Preparation of Thermal Head> Using such a sputtering apparatus 130, as shown below, a thermal head similar to that of the first embodiment (KGT-
260-12MPH8), a carbon protective film 90 was formed on the glaze surface to produce a thermal head of the present invention. That is, this thermal head also has a two-layered protective film including the lower protective film 88 of the silicon nitride film and the carbon protective film 90.

First, the substrate holder 13 in the vacuum chamber 132 is set so that the glaze faces the target material 114.
8, a thermal head 66 was fixed. The distance between the substrate (glaze surface) and the surface of the target material 114 was 100 mm. Further, similarly to Example 1, masking was performed in advance except for the glaze. After fixing the thermal head in this manner, the pressure in the vacuum chamber 132 becomes 5 ×
The chamber was evacuated to 10 ^-6 Torr. While continuing the vacuum evacuation, an argon gas is introduced through the gas introduction unit 134a, and the pressure in the vacuum chamber 132 is adjusted to 5.0 × 10 ⁻³ Torr by an orifice valve installed in the turbo pump.
It was adjusted to become. Next, a high frequency voltage is applied to the substrate by driving the bias power supply 150, and the lower protective film (silicon nitride film 88) is applied at a self-bias voltage of −200 V for 10 minutes.
Was etched. After the etching, a sintered graphite material as the target material 114 is fixed to the backing plate 154 (attached with In-based solder), and the flow rate of the argon gas is adjusted so that the pressure in the vacuum chamber 132 becomes 5.0 × 10 ⁻³ Torr. And the orifice valve is adjusted, and the target material 114 is
, A DC power of 0.5 kW was applied for 5 minutes. Next, while maintaining the pressure in the vacuum chamber 132, the target material 1
14 is 5 kW, and -20 is applied to the substrate.
After applying a high-frequency self-bias voltage of 0 V, the shutter 146 is opened, and at the same time, the flow of hydrogen gas is started from the gas introduction part 134b, and the carbon protective film 90 having a thickness of 1 μm is started.
Was prepared. Further, a thermal head having a carbon protective film 90 having a thickness of 2 μm and a thickness of 3 μm was manufactured in exactly the same manner.

Here, in the above example, the relationship between the hardness of the carbon protective film 90 formed in this system and the flow rate of hydrogen gas (ratio to the flow rate of argon gas) at the time of film formation is examined in advance. Accordingly, the hardness of the carbon protective film 90 to be manufactured was controlled. In particular,
In any of the film thicknesses of 1 μm, 2 μm, and 3 μm, the hydrogen gas flow rate at the start of film formation is 15% of the argon gas flow rate, and the hydrogen gas flow rate is continuously changed so as to be 5% at the end of film formation. Thus, the Vickers hardness at the start of film formation (inside) is 1200 kg / mm ² , the Vickers hardness at the end of film formation (surface) is 2200 kg / mm ² , and the hardness difference is 1000 kg.
A carbon protective film 90 whose hardness changes continuously at / mm ² was produced. Further, the film thickness of the carbon protective film 90 was controlled in advance by calculating a film forming speed, calculating a film forming time to obtain a predetermined film thickness, and controlling the film forming time.

<Evaluation of Performance> The same performance evaluation as in Example 1 was performed using the three types of thermal heads of the present invention. As a result, none of the thermal heads causes cracking or peeling of the carbon protective film 90.
Almost no wear was observed.

Example 4 The procedure of Example 3 was repeated, except that the target was changed to a glassy carbon material.
Three types of thermal heads each having a carbon protective film 90 having a thickness of 1 μm, 2 μm, and 3 μm were manufactured. Further, the control of the hardness and the hardness difference of the carbon protective film 90 was performed in the same manner as in Example 3. Specifically, in each of the three types of thermal heads, the hydrogen gas flow rate at the start of film formation is set to 15% of the argon gas flow rate, and the hydrogen gas flow rate is continuously set to 5% at the end of film formation. Vickers hardness at the start of film formation (inside) is 12
00 kg / mm ² , Vickers hardness at the end of film formation (surface) is 2
A carbon protective film 90 having a hardness difference of 200 kg / mm ² and a hardness difference of 1000 kg / mm ² and continuously changing hardness was used.

<Evaluation of Performance> Using the three types of thermal heads of the present invention, the same performance evaluation as in Example 1 was performed. As a result, none of the thermal heads causes cracking or peeling of the carbon protective film 90.
Almost no wear was observed.

In the same performance evaluation test, the etching was not performed; or only the pressure in the vacuum chamber 132 during the etching was changed to 8.0 × 10 ⁻³ Torr;
Alternatively, only the pressure in the vacuum chamber 132 at the time of film formation is changed to 3.0 × 10 ⁻³ Torr and 8.0 × 10 ⁻³ Torr; In the same manner as described above, various types of thermal heads prepared by forming carbon protective films of 1 μm, 2 μm and 3 μm were used. In any case, the same good results as those in Examples 3 and 4 were obtained. Was done.

[Comparative Examples] The following various thermal heads were prepared. a. Thermal head (KGT-260-12MPH8 manufactured by Kyocera Corporation) in each of the above examples b. The high frequency self-bias voltage during film formation is -200
Except that it was kept constant at V, it was produced in the same manner as in Example 1 and had a thickness of 2 μm and a Vickers hardness of 2500 kg / mm ^2.
Thermal head with a uniform carbon protective film. c. Except that the flow rate of the hydrogen gas at the time of film formation was kept constant at 5% with respect to the flow rate of the argon gas, it was produced in the same manner as in Example 3 and had a thickness of 2 μm and a Vickers hardness of 220.
Thermal head with a uniform carbon protective film at 0 kg / mm ² .

<Evaluation of Performance> Using the three types of thermal heads of the present invention, the same performance evaluation as in Example 1 was performed. As a result, the thermal heads of b and c
Before the recording of 000 sheets was completed, the carbon protective film was cracked or peeled off. In the thermal head a, abrasion of 2 μm occurred on the silicon nitride protective film. From the above results, the effect of the present invention is clear.

[0092]

As described above in detail, according to the present invention, corrosion and wear of the protective film are extremely small, and cracking and peeling of the protective film are also preferably generated against heat and mechanical shock. To realize a thermal head that has sufficient durability, exhibits high reliability over a long period of time, and can stably perform high-quality thermal recording over a long period of time. Can be.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example of a thermal recording apparatus using a thermal head of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a heating element of the thermal head of the present invention.

FIG. 3 is a conceptual diagram of an example of a (plasma) CVD apparatus for forming a carbon protective film of a thermal head according to the present invention.

FIG. 4 is a conceptual diagram of an example of a sputtering apparatus for forming a carbon protective film of a thermal head according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 (Thermal) recording device 14 Loading part 16 Supplying and conveying means 20 Recording part 22 Ejection part 24 Magazine 66 Thermal head 80 Substrate 82 Glaze layer 84 Heating resistor 86 Electrode 88 Lower protective film 90 Carbon protective film 100 (Plasma) CVD device 102 , 132 Vacuum chamber 104, 134 Gas introduction unit 106 Plasma generation means 108, 138 Substrate holder 110 Substrate bias power supply 112, 140 Exhaust means 114 Microwave power supply 116 Magnet 118 Microwave introduction tube 120 Coaxial converter 122 Dielectric plate 124 Radial antenna 130 sputtering apparatus 136 sputtering means 142 cathode 144 target material 146 shutter 148 magnet 150 bias power supply 152 DC power supply 154 backing plate

Claims (7)

[Claims] 1. A thermal head comprising a protective film mainly composed of carbon and having a hardness difference in a thickness direction as a protective film for protecting a heating element. 2. The hardness difference is 100 kg in Pickers hardness.
/ mm ² or more in the thermal head according to claim 1. 3. The thermal head according to claim 1, wherein at least one protective film mainly composed of ceramic is provided as a lower protective film on the heating element side of the protective film mainly composed of carbon. 4. A heating device according to claim 1, wherein a high-frequency bias voltage is applied to the surface of the heating element and the high-frequency bias voltage is changed in an atmosphere in which a gas containing carbon as a main component is ionized. A thermal head comprising a protective film having a difference. 5. An atmosphere in which a solid containing carbon as a main component is evaporated and a hydrogen gas is introduced, a plasma is generated on the surface of the heating element, a high-frequency bias voltage is applied, and a flow rate of the hydrogen gas is reduced. By making changes,
A thermal head, wherein a protective film having a hardness difference in a thickness direction is formed on a surface of the heating element. 6. A thermal head including a heating element is disposed in a chamber, and a gas containing carbon as a main component is introduced into the chamber, the gas is ionized, and a high-frequency wave is applied to the surface of the heating element. A method of manufacturing a thermal head, comprising forming a protective film having a hardness difference in a thickness direction on a surface of a heating element of a thermal head by applying a bias voltage and changing the high frequency bias voltage. 7. A heating head including at least a part of a thermal head including a heating element, wherein a solid containing carbon as a main component is evaporated while flowing hydrogen gas into the chamber, and the heating element is heated. A protective film having a hardness difference in the thickness direction is formed on the surface of the heating element of the thermal head by generating plasma on the surface, applying a high-frequency bias voltage, and changing the flow rate of the hydrogen gas. Method of manufacturing a thermal head.